The present invention relates to a sofa-bed with an articulated folding structure of the type defined in the preamble of claim 1.
It is known that sofa-beds with an articulated folding structure essentially comprise a fixed carrying framework to which three or more movable frames disposed consecutively and pivotally engaged with each other are linked. The movable frames are shiftable from a closed position in which they are folded over upon each other and housed within the fixed carrying framework thereby defining the conformation of a sofa-bed, to an open or unfolded position in which they are extended with respect to each other, thereby defining the conformation of a bed.
In this type of sofa-beds, the sofa back is generally fastened to the fixed carrying framework. This involves an important reduction in the space that the movable frames can use for entering the fixed carrying framework and coming out of same, during the closing and opening steps respectively of the sofa-bed. For the above reason, each of the movable frames is formed with a longitudinal extension greatly lower than that of the fixed carrying framework within which it is housed in the closed position. In addition, on passing from the closed position to the open position, the movable frames must carry out a starting movement involving a rotation and a translation with respect to the fixed carrying framework so as to reach a raised and advanced position relative to said carrying framework.
It is apparent from the above that in order to obtain a sufficiently wide bed, it is often necessary to use many movable frames folded over upon each other, as well as very complicated kinematic driving mechanisms. On the other hand, it will be also recognized that due to the presence of many movable frames, the thickness of a mattress disposed between said frames is to be greatly reduced, which brings about clear inconveniences from the point of view of the comfort offered by the mattress itself. It is also to be noted that the bulkiness of the sofa-bed when opened is caused not only by the bed framework, but also, although this is not actually necessary, by the sofa back which is rigidly associated with the fixed carrying framework, as above said.
In order to obviate the above drawbacks, the same applicant has recently developed a sofa-bed with an articulated folding structure in which the back structure is associated with one of the movable frames and not with the fixed carrying framework.
In addition, in order to enable the use of movable frames having sizes substantially identical to those of the fixed carrying framework, such movable frames have been connected to a pantograph linkage associated with the fixed carrying framework. Thanks to the above mechanism, the movable frames, before taking an extended configuration with respect to each other, carry out a starting vertical translational motion bringing them from the closed position to an intermediate position in which the movable frames, still folded over upon each other, are disposed above the fixed carrying framework. Under this situation, two movable frames of a longitudinal extension substantially equal to that of the fixed carrying framework could be used, thereby reducing the number of the necessary movable frames with respect to the known art, the bed sizes being unchanged.
Notwithstanding the clear advantages achieved, the above described sofa-bed still has problems and drawbacks from the operating point of view when passing from the closed position to the open position and vice versa. In fact, for opening the sofa-bed it is first of all necessary to lift the movable folded frames as far as an intermediate position above the fixed carrying framework is reached and, only afterwards, to cause their rotation with respect to each other until the unfolded position is achieved, in that the vertical translational motion of the movable frames is independent of the rotatory alignment movement of the same. In addition, once the set of movable frames has been raised, the use of a retaining device is necessary for ensuring the vertical locking of the set in the intermediate raised position in order to prevent the pantograph linkage from closing upon itself by effect of its weight. Finally, referring particularly to the closed position, it is to be pointed out that the steadiness in such a condition exclusively relies on a second retaining device, which brings about further construction complications. Due to the last mentioned reason the use of a mattress of high elastic stiffness is practically impossible, because such a mattress will tend to spontaneously extend and therefore will not be able to ensure a stable set up to the sofa.